A typical fire hose acting at a flow rate of 125 gallons/minute and a hydrant pressure of 110 psi will create a net rearward thrust that is on the order of 40 to 70 lbs. of force or more. This force must be resisted by a fireman holding the hose.
The effort required to control and contain such a hose is considerable. While the hose is on at full force, the thrust that must be absorbed is unremitting. Where a fireman is endeavouring to hold the hose directly in his hands, the muscles in the arms and hands of the fireman become fatigued. If a fireman's control over a hose declines sufficiently, a dangerous condition may arise when there is a risk that the hose may be dropped and thereby become freed to writhe and flail about.
Out of recognition of such risks a number of prior art patents have endeavoured to address this problem by providing firemen with devices to assist them in supporting a fire hose in operation:
U.S. Pat. No. 2,919,071--M. J. Dalton
U.S. Pat. No. 425,256--C. R. Robinson
U.S. Pat. No. 407,118--C. R. Robinson
U.S. Pat. No. 3,885,739--Phillip E. Tuttle
U.S. Pat. No. 1,829,621--G. L. Whiteford
U.S. Pat. No. 3,223,172--J. M. Moss
U.S. Pat. No. 5,052,624--Boers et al
U.S. Pat. No. 4,216,911--Huperz et al
The two Robinson references show the use of attachments in the form of anchored supports, that allow the thrust of a hose to be partially transmitted to the earth by a strut or post. Such arrangements, however, are of limited use where a fireman is continually moving to better reposition himself.
Whiteford shows the use of a convertible bar that can serve as a strut, as in the Robinson references, or permit two firemen to share in supporting a hose nozzle. While chains are provided in Whiteford to carry the weight of the hose, no provision is made to assist the firemen in absorbing rearwardly-directed thrust.
Dalton depicts a hand held pistol grip that attaches to a fire hose just behind a nozzle, allowing a fireman to absorb the thrust of the hose through the palm of his hand, rather .than through a grasping action.
Tuttle, like Dalton, depicts a pistol-grip arrangement, with a finger-operated valve added.
Moss addresses the problem of transferring thrust by providing a harness to be worn by a fireman, a series of nozzles being attached directly to the harness. This arrangement, however, lacks the flexibility of hand-control over a hose nozzle.
Two patents not relating to the fire hose application of the present invention are those to Huperz and Boers.
Huperz shows a nozzle with a pistol-grip and trigger arrangement as in Tuttle. Water is allowed to enter this nozzle system through the grip or handle. A cushioned "shoulder or arm rest" (19) is also shown as extending rearwardly from the nozzle/pistol-grip assembly, in the form of a single rod terminating in a curved and padded butt-end, which presumably may rest against a fireman's shoulder.
Boers also shows a nozzle with pistol-grip and trigger, water being fed through to the nozzle by a substantially linear rearward extension from the nozzle. Above this extension, a "shoulder rest" (26) is mounted at the end of an arm (27) that extends downwardly to fasten to the rearward extension behind the nozzle.
Both Huperz and Boers include a shoulder rest as part of an integral triggered nozzle assembly. However, this arrangement, in both cases contemplates applications involving small diameter, pressurized water-jets used for cleaning, rather than fire hose systems. One distinction, therefore, between these applications and that of the case of a fire hose is that the weight of water contained within the fire hose and the thrust developed will be far greater than that which would be present in a washing-jet nozzle.
A feature of the Huperz disclosure is that the "stock" on his nozzle-support system is mounted in-line with the nozzle. This directs the rearward thrust of the water jet directly against the Shoulder of the fireman, without developing any twisting couple arising from such thrust. A twisting couple may, however, as is subsequently shown, arise from the deflection of water within the hose and support itself.
Further, the Huperz arrangement requires the nozzle-support system to be elevated to shoulder level--an arrangement which would be fatiguing to a fireman holding a fire hose. By reason of the height of which the jet-gun of Huperz must be raised off of the ground, this design, if converted to pipes of the diameter required for fire hoses, would burden a fireman with lifting a heavy length of hose and water high off of the ground.
In Boers, the shoulder rest is elevated above the reaction line of the nozzle, allowing the sprayer to be located below shoulder level. A very slight downward bend appears to be depicted in the drawings in the Boers sprayer, rearwardly of the shoulder bracing plate. No reference is made, however, to this bend in the written disclosure. Further, based on the normal proportions of a user of the Boer's device, the hose coupling at the rearward end would appear to be positioned at a point which is behind the vertical plane defined by the rearward side of the user. These features will be contrasted with those of the present invention, discussed subsequently.
None of these references acknowledge that water changing direction as it flows around a bend will create an outward thrust. Depending on the location of this thrust, a twisting force or "couple" may be developed. This will be apparent to a user endeavouring to hold the fire hose as a tendency for the hose nozzle to deflect vertically from the direction of intended use. In the case of a fire hose these forces would be substantial.
There is a need, therefore, for a simple but robust type of support that can be readily adapted for use with typical existing fire hoses and nozzles and which will allow a fireman to absorb both the thrust created by the fire hose against his torso, and the torques that tend to cause the hose to twist, thereby reducing the fatigue experienced by the hands and arms of the fire fighter.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter.
These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. Such embodiments represent one example of how the benefits of the invention may be obtained. Other means for achieving the same effects will be apparent from an examination of the operations of the elements of such preferred embodiments.
The invention will then be further described, and defined, in each of the individual claims which conclude this specification.